A conventional portable communication terminal is described with reference to FIGS. 11 (a), 11 (b), 11 (c) and FIG. 12 which illustrate a portable telephone. FIG. 11(a) is a front view of the portable telephone in use. FIG. 11(b) is a side view of the same including a partial sectional view. FIG. 11(c) is a rear view of the same. FIG. 12 is a side sectional view of a transducer incorporated in the portable telephone.
In FIG. 11(a), on the front face of portable telephone 10, operating section 10a including pushbutton digits is prepared, and a transmitter (not shown) is also provided to the front face. Display section 10b including a liquid crystal display is disposed on an upper part of the front face, and a receiver (not shown) is provided to this upper part. In FIG. 11(c), opening 10c is provided on the rear face and guides the sound generated by transducer 11 to the outside.
A structure of transducer 11 is described with reference to FIG. 12. Circular diaphragm 1 generating aerial vibration is supported by frame 2 at its outer periphery with adhesive. Frame 2 includes a plurality of first sound-paths 2a. An end of voice coil 3 is rigidly fixed to a center portion of diaphragm 1, and both the ends of voice coil 3 are electrically coupled to terminal section 4 disposed at a lower end portion of frame 2.
A magnetic circuit formed of magnet 5, top plate 6 and yoke 7 is disposed in a recess provided at a center of frame 2. Voice coil 3 is inserted in a space (magnetic gap) between the outer periphery of top plate 6 and the inner wall of yoke 7.
Protector 8, to which second sound-paths 8a are provided, protects diaphragm 1, and forms a housing of the transducer together with frame 2. The foregoing portable telephone thus radiates only the sound delivered from second sound-paths 8a provided to protector 8 to the outside. On the other hand, the sound delivered from first sound-paths 2a provided to frame 2 is radiated within portable telephone 10. For that purpose, protector 8 is bonded to the inner wall of phone 10 via a spacer, so that transducer 11 is mounted in phone 10. This structure allows the sound delivered from first sound-paths 2a and the sound from second sound-paths 8a of protector 8 to be separated and free from interference.
The portable telephone has changed its function drastically from a telephone to an information terminal these days. This change entails the following requirements from the market: more sophisticated performances of the display such as a larger and color display, and better characteristics on an output sound-pressure from the display side as an interactive device. Further, a display of portable communication terminals such as portable telephones accompanies sound more often, such as reproduced sound of a video game, or a tone verifying a operation of pushed buttons.
Under these circumstances, reproduced sound by a conventional transducer or a conventional mounting structure of the transducer in operating the display lowers a directivity toward the front side of the communication terminal due to diffraction effect, because the sound is delivered only from second sound-paths 8a. Thus, sufficient volume and quality of sound cannot be expected to the front side of the portable telephone. The present invention aims to provide a portable communication terminal that overcomes the foregoing problems.